In recent years, the practice of removing undesirable tree stumps has been revolutionized by the introduction of stump cutting machines. Stump cutters typically utilize a gasoline or diesel engine to rotate a cutter wheel that grinds tree stumps into chips. Generally, power is transmitted from the engine to the cutter wheel via a drive train consisting, at least in part, of pulleys and belts and/or sprockets and chains.
Larger stump cutters typically have a two-stage cutter wheel drive train. Both stages may consist of a system of pulleys and belts, or the like. Alternatively, the first stage may consist of a hydraulic pump and motor system. Smaller stump cutters tend toward a single stage drive train which may be either a belt and pulley type system, or a hydraulically driven system.
The cutter wheel is typically attached to an axial shaft supported by two sealed bearings disposed on opposite sides of the cutter wheel. The final driven sprocket, or a hydraulic motor, is usually mounted at one end of the shaft.
The current drive configurations suffer from a number of drawbacks and limitations. Belts, pulleys, and the like, require that proper tension and alignment be maintained. In a drive train where both stages consist of belt and pulley systems, altering the tension or alignment at either of the stages affects the other stage, the components of which must then be readjusted. Substantial shielding of belt drives is also required, which can limit visibility during the cutting process. Avoiding interference of the shielding with machine components or other obstacles may also limit the cutting range of the stump cutter.
Hydraulic motors mounted on the cutter wheel shaft are vulnerable to damage unless shielded. This may add significant bulk in the area of the cutter wheel shaft, which can limit the cutting range of the stump cutter. In general, hydraulic drives are more expensive than mechanical drives and they typically deliver a lower percentage of engine horsepower to the cutter wheel.
With most current designs, the cutter wheel support bearings each have two seals, one on each side of the rolling elements. Occasionally, replacement of the cutter wheel bearings is required because debris damages the grease seals or works past the seals into the rolling elements of the bearing. Also, these bearings typically require manual relubrication periodically; failure may result from heat build-up due to insufficient or excessive lubrication. Bearing, cutter wheel, or cutter wheel shaft removal/replacement usually requires removal of the assembly comprised of the cutter wheel and shaft, two bearings, and the driven sprocket/pulley, or the hydraulic motor. Beating removal from the shaft is often a difficult process resulting in damage to, or destruction of, the bearings and/or shaft. Reassembly requires realignment and retensioning of final drive pulleys, belts, etc.
A stump cutter unit powered by a farm tractor power take-off shaft is also known in the art. One major disadvantage of this unit is that the tractor itself must be repositioned to move the cutter wheel from side to side over the stump surface.
Those concerned with these and other problems recognize the need for an improved stump cutter.